Electrical circuit and apparatus



June 18, 1935. J. w. DALTON ELECTRICAL CIRCUIT AND APPARATUS Filed July 19, 1932. 2 Sheets-Sheet l June 18, 1935. J. W. "DALTON 2,005,130v

ELECTRICAL CIRCUiT AND APPARATUS Filed July 13, 1932 2 Sheets-Sheet 2 anual? a 111 -lifi:

Patented June 18, 1935 PATEN T OFFICE- ELECTRICAL CIRCUIT AND APPARATUS John" Willey Dalton, Wimbledon, London, England a Application-July 19, 1932, Serial No. 623,426

In Great Britain July 28, 1931 v v I 1 Claim. This invention relates to the production of representations of original subjects, for instance printing plates or like surfaces, by electrically controlled means and extendsto the production of such visual representations at a station distant from that at whichthe original subject is located, or in other words, by methods falling within the scope of the term phototelegraphy. The invention relates, inter alia, to theproduction of engraved surfaces adapted'for use, for instance, in substitution for photo-mechanically produced surfaces or blocks, the original and the surface to be engraved, for example, being operated upon at the same station or, in other words, in conditions which do not correspond with those obtaining in photo-telegraphy.

The invention consists in a method of producing a representation of an' original subject which comprises applying a gradually decreasing negative voltage to the grid of a gaseous discharge tube during regularly spaced predetermined intervals of time, .projectinglight on to successive small areas of the original subject in a scanning operation during a fraction of eachsuch interval, causing the light reflecte-d from or transmitted through each such small areacf the original sub- 59Gb to set up a voltage on thegrid of the tube proportionate with'thetone values of the successive small'are'as into which the original subject is scanned, applying a plate voltage to thetube which is interrupted at the end of each such interval, and causing reproducing means, for instance a cutting tool, to be actuated by the plate, current flowing through the tube from the instant atiwhich the grid voltage reaches a predetermined value permitting the flow of plate current .tothe end of each such predetermined interval 1 l Conveniently'the gaseous discharge tube may beia Thyratron tube (the name Thyratron being a registered trade-mark), one of the properties of which is to preclude the now of current from the cathode to the anode until the grid of tubehas been given a certain minimum negative bias and thereafter to permit the flow of current irrespective of variation in the bias until the operation of the tube is interrupted by change in the voltage applied to the anode.'

' The interruption of the flow of current in the anode circuit may be effected by the employment of, a mechanical interrupter, or alternatively by applying an alternating or otherwise varying voltage to the anode circuit of the tube from some convenient source of current of the desired character.

The invention will be described further in de tail withreference to the accompanying drawings in which are illustrated diagrammatically and by way of example certain forms of apparatus in accordance with the invention:

Figure 1 being a view partly in perspective and partly diagrammatic of one construction,

Figure 2 beinga corresponding view of a second construction. In Figure 1 I indicates the original of which 10 an engraved reproduction is to be formed mounted upon a support 2 freely movable upon the upper platform 3 which is connected by the vertically arranged portion 4 with the lower platform 5 upon which a table 6 adapted to form a support 15 for the surface I to be engraved is arranged in association with guides 8 permitting the table 6 and with it the surface 1 to beengravedto be moved in one direction through the intermediary of the lead screw 9.. This lead screw is connected 20 with the spindle l0 ofthe motor II also acting as a I convertor which, with the guides andilead screws, is mounted upon a table l2 in association with guides is secured to the platform 5. This table, in turn, is adapted to bemoved in a stepwise 5 manner in a direction at right angles to the direction in which the table 6 is moved on its guides 8, such motion being secured by the lead screw I 4' which is provided with an extension l5 rigidly connected with a ratchet wheel is co-operating 0 with pawls ll on the toothed wheel I8 rotatably mounted upon the aforesaid extension of the lead screw.

With the toothed wheel in question is engaged a rack l9 connected with a core 20 arranged with-,

in a solenoid H the energization of which,in a manner subsequently to be described, will cause stepwise vmotion to be. imparted to the lead screw at determined intervals of time.

The operation of the motor Ill will cause the table 6, in consequence of the action of the lead screw 9, to travel in a direction parallel with the axes of the guides 8 in one or other of two senses until one or other of the pins 2Zis brought into position to actuate a switch 23 comprising a movable contact 24 and two fixed contacts25 and 26, thus causingthe movable contact to complete the circuit through one orother of the fixed contacts and thus through the leads 2! and 28 with the winding 29 of the motor H, the mid-point of which is connected with a lead 30, supplying direct current to the motor, and the brush 3i associated with the' commutator 32, the other brush 33 being connected with the lead 34 of the supply of direct current; The alteration of the position ate-one or other of the passing to of this switch will change the direction of rotation of the motor I l on the shaft of which is also provided a friction-operated double pole phase reversing switch 35 connected by the leads 36 with the three-phase self-synchronizing motor 31 in such manner that the reversal of the direction of rotation of the motor II will not result in a similar reversal of the direction of rotation of the motor 31. v

On the spindle of the motor 31 there is mounted a light-interrupter disc 38 through which is projected light from a source 39.

In the interrupter disc there areiprovided two sets of apertures 40 and 4 I, thelatter being in the path of the rays directed on to a prism t2 from which they are directed in turn on to the lightsensitive surface 43 in circuit .with a-valveamplifier 44 and rectifier 45. The other setof apertures 40 is arranged in the path of the light rays the lens 46 by which they are directed onto theoriginal I, the light reflected from the originalbeing; in turn, reflected-by the mirror-41 onto the light-sensitive cell 48 connected'with the valve amplifier .49, and rectifier 50.

For the purpose ofensuringthat to the original I ,motion is imparted correspondingewith that imparted .to'the. engraved surface, .a .pantograph .device is employed. --In the construction illustrated, the pantcgraph comprises a rod 5| ,mounted in a ball-and-socket joint 52 on the bracket :53, the height of which can be variedby engaging bolts 5,4 in one or other of the rows of holes .55.

It .will be appreciated thatat intervals motion must be imparted to the table 6 to secure :its movement in a direction at right angles to the axes of the guides B .as has in fact been already stated ,This' motion is secured as the result of one or" other of the pins 22 beingcaused topperswitches 56, 51 in circuit with ,the solenoid 2|, thesolenoid being thus energized at intervals whereby the core of 'the solenoid will .be causedcto move to a degree limited by the set screw v5,8 to-advance the table in the direction in question a predetermined distance. f v

The .output from the rectifier-.50 is applied across the condenser 59 arranged-in the grid lead of a Thyratrontube orother form of gasfilled relay Bil, the anode of which isconnected with thesecondary 5 I of ,a transformer, the primary 6 2 of which isconnected by two leads to the three phase synchronous motor ,.31. The secondary in question is connected through. the condenser 63 with the fila ment battery -54 -of the ffhyratron tube, a, form of gas-filled relay tube, with a grid biasing battery 65 and also with a. source of direct current 6 6,.one terminal of which is connected by the lead lfl'withflone end of the winding .68, theotherend of which is connected by the lead 69 with one end of the secondary 6i which is also .connectedby the lead 10 ,withthe anode, of the Thyratron tube.

The rectifier .45 is connected by the leads 1| across, the resistance v,12 connected to one electrode f the condenser 59, and with the secondary :13 of the transformer of whichthe primary is indicated by the reefrence $2.

The current; supplied to. the Thyratron tube will be controlled by the outputs of the lightsensitive cells and in accordance .with the currentgflowing in the anode circuit. The core 14 arranged in the winding ,68 willbe moved for a greaterlor less length of time into. the position in which it closes the ballva1y e/15. provided in the casing 16 in .which a rotarypump. 11 ,is-arvvance the, point of the engraving tool 8| for a greater or less length of time or less distance into the surface of the plate to be engraved.

The-depressions formed in the engraved surface will thus be controlled in ;magnitude in relation to the tone value of the corresponding area of the original.

In the construction illustrated in Figure 2, the

original is indicated by the reference 82 and it is mountedupona mandrel .33 securedbnsa lead screw 8.4.on which also amandrel .85 is secured carrying the surface .86 to be engraved, the lead,

screw being driven throughgearingv arranged ,in the casing ,81 bythe motor 58.. which,also,drives the shaft 89 on ..which the interrupter disc-.30 ismounted. On this shaft there vis also mounted a. movable contact 9i co-operating .withlcontact segments 92 and .a further contact memherifl co-operating with, a 1. contact 84 and ,a plurality ofstuds -95. p

,Light isprojected ontoithe original from. the source of illumination 36 through apertures in the interrupter disc .90, the light passingtthere through being concentrated by thelens {81 .and projected on to theoriginal 82,.the light reflected-f cm wh h in turn, r flec e by thei-l n 38 on to the'light-sensitive cell 93, theflcurrent flowin th ou w h-isamp ified by thevalv am lifier 1.0.0 in th output of which is. arran e the p ima y- 01 vof th transform r, on .endpf. h s conda H of .whicha connected throush he e tifi 10 th the rido th T y atro tube, .194 and also with the condenser L05, vthe o he end f t seco dary bei connected with he po ite e m ,o the condcnserand-with h n t men the tuds 35 as ociated w the gme t bein connec ed o ether u h e tance an wi h. a sou cecfjiiirect current indicated by g the negative terminal jot the battery. I06, he positive terminal of which is connected through the whole of the resistance with one of the studs, the leadlll lbeing taken fro n h Qf tud o th efilamen heating battery I08 connected acro'ssthe filament of the Thyratron tube and also to 'one'ter minal of a. second battery 109, the other end ,of which is connected with one end of the solenoid 119, the other endofthe solenoidbeingwconnected .with one ,of the segments ;9 2, the other segment being connected, in turn, with the anode of the Thyratron tube. H

Within .the solenoid up there is arranged a core Ill provided withan extension H2 adapted, by the movement of the solenoid, to actuate .a ball valve H3 associated with the chamber I M in which there is contained a liquidand into the chamber containing the liquid extends a piston elem n N5 th n o wh h wn ac swith a am on h ha t 8.9.

Rotation of the shaft will cause the pist qn eledepth or otherwise in I therein to move the stem H8 of the engraving tool H9 in opposition to the spring I20, thus causing the engraving tool to make an impression of greater or less depth in the surface to be engraved proportionate with the amount of light reflected from the corresponding surface of the original.

The mandrel 82 on which the original is mounted, and the mandrel 85 with which the surface to be engraved is associated, may be moved continuously or in a stepwise manner.

While above the invention has been described mainly in its application to the production of engraved surfaces, the invention as stated extends to the production of visualrep resentations of an original generally and by for instance methods falling within the scope of the term photo-telegraphy.

In conclusion it is to be observed that the foregoing description is furnished for the purpose of illustrating certain suitable manners of carrying the invention into effect and various changes may be made in the details of construction and arrangement above referred to without exceeding the scope of the present application. For instance, while particular circuit arrangements and modes of operation have been described in some detail it is to be understood that the individual features of such circuits or modes of operation may be employed in combination or association with features herein referred to other than such as are specified in their immediate context, without departing from the invention.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:-

The method of producing a representation of an original subject which comprises moving the original subject relative to scanning means, moving a surface upon which the representation of the original subject is to be formed at acorresponding rate relative to reproducing meanaand during such movement effecting in each of a plurality of successively recurring regularly spaced intervals of time the following operations:applying to the grid of a gaseous discharge tube for a period of time which is constant for each of the-intervals a decreasing negative voltage the rate of decrease of which is the same for each of the intervals, projecting light on to a small area of the original subject in a scanning operation during a fraction only of the said period, applying to the grid of the tube during the said fraction of the period a further voltage which is stored on the grid and is proportionate with the tone value of the light transmitted through or reflected from the small area as a result of the scanning operation, thereby causing the voltage on the grid to reach a value permitting the flow of plate current only after the lapse of a fraction of the time interval which is proportionate with the tone value of the small area, causing the reproducing means to operate upon the surface upon which the representation is to be formed by current flowing from the plate of the tube from the instant at which the grid voltage reaches the said predetermined value to the end of the interval, and at the end of the interval interrupting the flow of current from the plate of the tube, thereby interrupting the operation of the reproducing means.

JOHN WILLEY DALTON. 1 

